Last summer Bill Gates and his foundation held a competition to reinvent the toilet. Now he's hoping to do the same for condoms.

The Bill & Melinda Gates Foundation is putting up $100,000 to the best proposal for a more fun and pleasurable condom.

The competition is part of its Grand Exploration Challenges, which has already doled out nearly $50 million for quirky but effective solutions to global health problems, like microwaves to treat malaria and an electronic nose to detect tuberculosis.

But why do condoms need revamping? Well, modern condoms have some great assets. They're cheap, discreet and prevent sexually transmitted diseases, including HIV.

But the Gates Foundation, which supports NPR, says that a lot of men perceive them as interfering with the pleasure of sex, and that means they won't use them consistently. (The condom "gap," or shortages, is another problem in a lot of developing countries, according to the United Nations.)

So the foundation is calling for new shapes, materials and packaging that "significantly preserve or enhance pleasure, in order to improve uptake and regular use."

Trojan and Durex have been trying to do this for decades with ribs, contours and lubricants.

But "we know empirically that those don't work as claimed," the Gates Foundation's Stephen Ward recently told the Humanosphere blog. "The idea here is to seed innovative ideas."

To get a sense of what kinds of ideas they're keen on, have a look at the post he and a colleague recently wrote on The Impatient Optimists blog.

First, there are the ORIGAMI Condoms. Shaped like miniature accordions, these silicone rubbers fit loosely and aim to simulate the feeling of sex without a condom. They also boast a 2.8 seconds "application time," the company's website says, which presumably means they go on easily.

Others are searching for a solution for the ladies. Bioengineers at the University of Washington have developed a super fine cloth that slowly releases spermicides and anti-HIV drugs. The material, which self-assembles in an electric field, could coat a vaginal ring or get inserted inside a woman, the inventors recently wrote in the journal PLoS One.

Although the first female condom didn't appear until 1993, male condoms date back to at least the 16thcentury, when the Italian physician Gabriele Falloppio advocated a linen cloth soaked in chemicals to prevent syphilis. Over the next few centuries, condom material evolved from animal intestines and bladder to rubber and then latex.

But since the 1920s, the technology has changed little, Ward tells Humanosphere, while material science, neurobiology and medicine have come a long way during this time.

That's also why the $100,000 condom challenge is open to anyone who can come up with a game-changing condom design in two pages by May 7, 2013.